Liquid circulating system



AW 1 -F. w'. DAVIS 2,251,564

'LIQUID CIRCULATING SYSTEM Original Filed June 20, 1936 v 07-14 a; fl 1/05/772 Patented Aug. 5, 1941 Application June 20, 1936, Serial No.86,31 Renewed January 20, 1940 Claims. iol. 60'- 52) This inventionrelates to apparatus for improving the action of a liquid. circulatingsystem wherein a substantially constant quantity of liquid is circulatedcontinuously through a circuit including a pump and a motor.

The invention more particularly relates to circulating systems adaptedto be carried on vehicles such as automobiles for the operation of oneor more mechanisms thereon such as a power steering gear, power-actuatedbrakes, doors on busses, and the like. It is convenient in such cases todrive the pump of the, system by some moving part of the motor whichdrives the vehicle, as for example the cam shaft. It is evident that,owing to the various speeds at which the vehicle maybe operated,the-'pump will ordinarily be operated at widely difiering speeds. Whenthe vehicle is traveling at a high rate of speed, the pump will beoperating at a proportionally high speed. This may result in cavitationat the suction side of the pump, particularly when the to make good anyliquid which may be lost by leakage or otherwise. I

For the escape of air, valve means are provided by which the stream ofliquid approaching the suction side of the pump may be by-passed partlyor wholly through the reservoir. This gives liquid is relatively thickor sluggish. Such a con- 7 dition is liable to occur when an automobileis first started .up and where the circulated liquid is oil which iscomparatively thick and viscous when cold.

It is an object of the present invention to prevent cavitation at thesuction side of the pump even when the pump is operating at very highspeeds. It is a further object of the invention to provide means forridding the system of any gas or air bubbles which may get into theliquid stream.

Such bubbles foster a tendency toward cavitation maintain the liquid inthe suction line at a pres- 4 sure considerably higher than'it wouldhave ordinarily. To this end, a reservoir is provided for excess liquid,this reservoir communicating with the injector device so as to'maintaina constant head of liquid therein. The injector tends to suckliquid from the reservoir, but, since the liquid passing through theinjector nozzle represents substantially the entire discharge streamfrom the pump, the liquid actually drawn When the bubbles of air or gasare' the bubbles a chance to rise in a comparatively quiet pool, andthus to escape from the top of the reservoir. 1

For a more complete understanding of the invention, reference may be hadto the description of certain'embodimen'ts thereof which follows, and tothe illustration thereof on-the drawing of which-- Figure 1 is anelevation of a liquid circulating system embodying the invention.

Figure 2 is a sectional view of the reservoir and-a portion of theapparatus associated therewith.

Figure 3 is a section on the line 3-3 of Figure 2.

Figure 4 is a fragmentary sectional view of a modified form of valvemeans.

Figure 5 is a section on the line 5--5 of Figure 2.

In Figure 1, a fluid pump, preferably of the gear type; is indicated atIll, this pump having a discharge line H leading to afluid motor I2. Themotor is preferably of a type permitting a through flow of the powerfluid at all times, both when the motor is operating and when it is atrest. A motor of this type is described and illustrated in my Patent No.1,790,620. After passing through the motor l2, the fluid returns througha. suitable pipe ll to the suction side of the pump. 4

Th rpipe ll leads to a passage [6 (Figure 2) which in turn dischargesthrough a nozzle l8 into a chamber 20 from which leads a passage 22 tothe suction side of the pump II. The nozzle ll tapers somewhat so thatits orifice 2| is reduced in cross section. Directly opposite thisorifice ll is the orifice of the suction passage 22.- The reduction ofthe cross section-of the nozzle [8 results in the projection of a. highvelocity jet of liquid into the suction passage 22.

5 The suction passage 22 increases in cross section being employed toboost the pump'and to prefrom the reservoir is only that which isrequired to vent cavitation at the suction side thereof whenthe'pumpisrunningathighspeed. Theehamber 20 is maintained full of liquidby a connection with a reservoir ll conventio a located above thechamber so that the gap between the orifice 24 ofthenomleand theoriflce20 ofthe pipe leading to the suction end of the pump is alwayssurrounded by a yielding liquid seal. To

In order to get rid of air in the system when 7 liquid is firstintroduced thereinto after the system has been drained, and to maintainthe system free from small entrained gas bubbles, a two-way valvemechanism may be provided as illustrated in Figure 2. As therein shown,the passage 15 leads into a valve chamber 40. A valve member 42 isvertically movable within this chamber. The upper end of the chambercommunicates with the interior of the reservoir as by a number of ports44. The lower end of the chamber opens directly into the nozzle 18, atthe upper end of which is a valve seat 45. When the pump is not inoperation, the valve member 42 rests on the seat 48 by its own weight.This may be augmented by a suitable spring 50. which, as shown, may bearagainst the upper end wall of the chamber at one end and against thevalve itself at its other end, the valve member being hollow as at 52 topermit the use of a relatively long spring. The valve member 42 has areduced external diameter at its mid-portion, the upper end portion 54 bng a flange which fits slidably in the upper portion of the valvechamber but which is partly cut away as indicated at 56 in Figure 3 topermit limited flow of liquid from the passage 15 up through the ports44 into the reservoir. Figure 2 shows the valve in its lower portionseated on the seat 48 so as to cause all of the stream entering throughthe passage 15 to flow up through the ports 44 into the reservoir andthence down through a passage 32 into the chamber 20 and the suctionline 22. In order to prevent splashing in the reservoir, a baflie 50 maybe mounted over the ports 44, this bafile being provided with one ormore small holes 62 to permit the escape of air or gas which mightotherwise collect under the bafile.

The lower portion of the valve member 42 is accurately ground to seatsnugly on the seat 45. The portion 64 of the valve member, immediatelyabove its seat-engaging portion, is of suflicient diameter to engageloosely the walls of the chamber 49 and center the valve member, thisportion being notched, as indicated in Figure 5, to permit free accessof fluid to the under face thereof at all times. The valve member 42occupies the position shown in Figure 2, when the flow of liquid throughthe passage I6 is of insufficient velocity to raise the valve from itsseat. The spring 50 is preferably such that, when the pump is running atlow speeds, the valve will be in the position shown in .Figure 2, thuscausing the v liquid to be bit-passed through the reservoir whereentrained air bubbles can readily escape. When the pump is speeded up,however, so that there is danger of cavitation at the suction sidethereof, the increased velocity and pressure of the stream in thepassage l6 act on the under surface of the flange 54 to raise the valve42. As soon as the valve is raised from its seat, the liquid pressurealso acts on its lower end to force the valve up against the upper endof the end wall of the chamber 40, thus closing the ports 44 andpreventing the further flow of liquid into the reservoir. Thus, as longas the high velocity of flow is maintained, the stream will be directedthrough the nozzle 18, and the increase of velocity of the stream as itleaves the nozzle will be utilized to raise the pressure within thesuction line 22 and thereby to prevent cavitation.

Figure 4 illustrates a modified form of valve mechanism which can beemployed to relieve the system of entrained air or gas bubbles. Asshown, a valve member "H! is mounted on the lower end of thescrew-threaded shaft 12 having a polygonal head 14 to receive a suitablewrench. Manual rotation of the threaded shaft 12 moves the valve up ordown to close the ports 44, as illustrated in Figure 4, or to engage theseat 46 so as to divert the stream from the passage I6 through thereservoir. When the system is first filled with liquid, the valve ismoved down against the seat 46 so that the air in the system can readilyescape through the reservoir. After the air has been driven out of thesystem by operation of the pump for a suitable period, the valve israised manually to the position illustrated in Figure 4, whereupon thesystem is ready for regular operation. In case air bubbles get into thesystem, they can readily be removed by moving the valve 70 against theseat 46 for a short period during which the pump is operated tocirculate the liquid through the reservoir.

It is evident that variou mod fications and changes may be made in theparticular embodiments of the invention herein shown and described,without departing from the spirit or scope of the invention as definedin the following claims.

I claim:

1. In a liquid circulating, system, a pump, a fluid motor, a dischargeline leading from said pump to said motor, a suction line leading fromsaid motor to said pump, a reservoir communicating with said suctionline and adapted to maintain a liquid head in said suction line when thepump is not operating, and means for utilizing the velocity of'liquidreturning from said motor to maintain in said suction line during theoperation of the pump a pressure exceeding that of the liquid head plusatmospheric pressure.

2. In a liquid circulating system, a pump, a fluid motor, a dischargeline leading from said pump to said motor, a suction line leading fromsaid motor to said pump for the continuous circulation of a constantquantity of liquid through said pump and motor, a reservoircommunicating with said suction line and arranged to maintain a liquidhead'therein when the pump is not in operation, and means for utilizingthe circulating stream from the motor to maintain in said suction lineduring the operation of the pump a pressure exceeding that of saidliquid head plus atmospheric pressure.

3. In a liquid circulating system, a. vented reservoir at the high P intof said system, a chamber, a passage leading from said chamber, a.nozzle projecting into said chamber and arranged to direct a jet intosaid pasage, a permanently open passage from said reservoir opening intosaid chamber beside said nozzle whereby a liquid head is maintained insaid chamber, a supply pipe opening into said nozzle and said reservoir,

and valve means for directing the stream in said supply pipethrough saidnozzle or into said reservoir.

4. In a liquid circulating system, a pump adaptedto be operated atvarious speeds, a disflow is high and to by-pass the flow through thereservoir when the velocity of flow is low.

5. In a liquid circulating system, a pump having a discharge and asuction, means for returning to said suction substantially the entirestream of liquid passing through said discharge, said means including achamber, a suction pipe leading from said chamber to the suction side ofthe pump, a nozzle projecting into said chamber, means for directingsubstantially the entire discharge stream from the pump through saidnozzle, and a reservoir above said chamber open to the atmosphere andcommunicating with said chamber.

6. In a liquid circulating system, a pump having a single discharge lineleading therefrom and a suction line leading thereto, a Venturi deviceconsisting of a chamber opening into said suction line and a nozzleprojecting into said chamber, means connecting said nozzle with saiddischarge line so as normally to direct the entire stream from-the pumpthrough the nozzle, a by-pass around the nozzle leading into saidchamber and including an open reservoir above the nozzle, and a two-wayvalve automatically operated by the stream from the discharge line todirect said stream through the by-pass when the pump is operating at lowspeeds and to direct the stream through the nozzle when the. pump isoperating at high speeds.

7. In a liquid circulating system, a pump, a motor, a discharge pipeline'irom said pump to said motor, a return pipe line from said motor tosaid pump for the continuous circulation of a constant volume of liquidin said system, and means for boosting the liquid pressure at thesuction 'end of said pump, said means comprising a Venturl device insaid return line and a yielding liquid seal for said device.

8. In a liquid circul' ting system, a pump, a motor, a discharge pipeline from the pump to the motor, and a return line from the pump to themotor for the continuous circulation of a constant volume of liquidthrough the system, said return line comprising a chamber, a pipe fromsaid motor terminating in a nozzle with a reduced orifice within saidchamber, a pipe connecting said chamber with the suction end of saidpump,

' the entrance orifice of,said last-mentioned pipe being directlyopposite the orifice of sai nozzle, and means for maintaining a yieldingliquid seal around the gap between said orifices.

9. In a liquid circulating system, a pump,

means for conducting substantially the entire stream of liquiddischarged from said pump back to the suction end or the pump, saidmeans comprising a chamber, a short pipe leading from said chamber tothe suction end of the pump, said pipe having an orifice of reduceddiameter opening into the chamber, a nozzle within said chamber directedtoward said orifice, the extremity of said nozzle being near saidorifice and having an internal diameter substantially equal to that ofsaid orifice, and means for conducting substantially the entire streamdelivered from the pump to said nozzle to be discharged therethrough,and means for maintaining said chamber filled with liquid.

10. In a liquid circulating system, a pump, a chamber, a shortpipeextending from said chamber to the suction end of saidpump, saidpipe opening into said chamber .with an orifice of less area than thatof the cross-section of the interior of the pipe, a nozzle having adischarge orifice of substantially the same size and shape of said pipeorifice directed toward said pipe orifice, means for conducting to saidnozzle substantially the entire discharge stream from said pump, andmeans for maintaining in said chamber a body of liquid surrounding saidorifices.

FRANCIS W. DAVIS.

